The Saccharimeter is a device for measuring the rotation of
the plane of polarization of liquids. Polarized light produced by the Nicol
prism on the right-hand side of the apparatus travels through the empty
glass cell, and a second Nicol prism on the left-hand side is rotated until
the light (usually the yellow light from a sodium lamp) is extinguished.
The liquid sample is placed in the cell, and the amount by which the Nicol
prism has to be rotated to get extinction once more is noted. This angle
is a linear function of the concentration of the sample. The original work
was done by Jean-Baptiste Biot (1774-1862) in the 1830s.

Saccharimeters get their name from their use in

distinguishing between sugars which produce right-handed rotation of the
plane of polarization (dextrose) and left-handed rotation (levulose or
fructose). They were basic instruments in chemistry laboratories, and are
not very often found in physics laboratories. The instrument above is at
Kenyon College, and dates from the end of the 19th century. I have used
it a number of times in upper-division optics laboratories, perhaps because
it was available.

The saccharimeters below, all by Duboscq of Paris, are
in the collection of the United States Military Academy. The middle one
is an 1845 design by the French instrument manufacturer Jean-Baptiste-François
Soliel (1798-1878), whose business was taken over in 1849 by his former
apprentice and son-in-law Jules Duboscq. The transverse white mechanism
on the right-hand side is a pair of quartz wedges, one cut to rotate plane
polarized light to the right and the other one to the left. These are slid
back and forth until the rotation caused by the liquid is cancelled.

This handsome Soleil-type saccharimeter is in the Garland
Collection of Classical Physics Apparatus at Vanderbilt University. It
was bought from the firm of J. Duboscq of Paris about 1875.

The eyepiece is missing, but the apparatus is otherwise
complete. The right-hand side of the mechanism can be slid back and forth
to accomodate sample tubes of various lengths.